Hook and loop connector pieces having a plurality of hooking elements made in one piece in the form of stalks with thickenings and located on the hooking or front side of the support strip are conventional. A production process for producing the support strip of these hook and loop connector pieces is described in DE 198 28 856 C1 (corresponding to U.S. Pat. No. 6,627,133). In this process, preferably a thermoplastic, especially a polyolefin or polyamide, in the plastic or liquid state is supplied to a gap between a pressing tool and a molding tool. The shaping element on the molding tool is a screen with continuous cavities. The hooking elements are formed by the thermoplastic which at least partially hardens in the cavities of the screen. In this way, a micro-hook and loop fastener with 200 to 400 hooking elements per cm2 is formed. Instead of the mushroom-shaped hook and loop elements formed in this connection, a support strip can also be provided in the form of a textile material in which the hooking elements are formed by a loop material which is, for example, integral with the textile support strip. Instead of the loop material, a fleece or mushroom structure can also be used.
These hook and loop connector pieces are used for diverse purposes, for example, in motor vehicle engineering, floor installation technology, clothing of any type, and special applications in mechanical engineering. The hook and loop connector pieces have proven themselves in these areas as a detachable and reliable connecting and closing technology. If these hook and loop connector pieces are used for aircraft or vehicle passenger seats, they are used among other purposes to attach seat coverings to foam body parts, ones formed of a molded foam. Some hook and loop connector pieces are foamed into the cushion foam material when the respective seat is being produced. The hook and loop connector piece with the corresponding hooking elements is fastened to the upholstery material, in particular sewn to it. For the purpose of producing the foam body parts, the hook and loop connector pieces are inserted into seating pipes of a foam mold. By insertion of foam material into the free cross sections of the foam mold, preferably polyurethane (PU) foam, the hook and loop connector pieces are fastened to the foam body parts in the process of foaming-in. The parts employed normally project above the other walls of the foam mold, and thus, later form groove-like recesses in the foam body part which is then engaged in the upholstery material with the other corresponding hook and loop connector piece. In this way, geometric seam and shape patterns may be produced on a particular seat depending on the design.
DE-A-100 39 940 (corresponding to U.S. Pat. No. 6,537,643) discloses a generic hook and loop connector piece with a support strip with hooking elements located on it. A cover strip covers the support strip on the side facing away from the hooking elements, and is wider than the support strip so that free side edge areas of the cover strip extend on both sides beyond the longitudinal edges of the support strip. In the known solution, the two free side edge areas of the cover strip are folded around one another such that the end edges of the free side edge areas are facing the longitudinal edges of the support strip. The cover strip on both sides then forms a sealing lip extending along the area having the hooking elements and adjoining the wall parts of the foam mold which surround the mold trough in which the hooking elements are held during the foaming process. The foam material introduced into the foam mold causes this sealing lip to be pressed against the facing wall parts of the mold. The sealing lip, due to a certain flexibility in the area of the fold line, conforms to the wall areas which form the sealing surfaces, so that improved sealing action of the foam barriers is achieved.
Moreover, in the known solution, the support strip can have at least one flexurally stiff reinforcing element extending preferably in the form of a bending wire along the support strip. In foam molding, better embedding properties for hook and loop connector pieces result. Due to the flexural stiffness of the reinforcing element, the hook and loop connector pieces, once inserted in the respective foam mold, remain in their position.
Furthermore, in the known solution the cover strip is formed from a plastic nonwoven to enable good crosslinking with the polyurethane mold foam for producing cushion parts in motor vehicle seats. Especially under subsequent high stress in daily use of the seat, this adhesion is often not adequate and detachment of the hook and loop connector piece from the foam cannot be precluded.
In order to counteract this inadequate adhesion, U.S. Pat. No. 4,693,921 discloses anchor elements attached on the back of the support strip with the hooking elements, with projecting anchor parts to improve adhesion to the molded foam. In practice, in spite of these anchor elements, improved adhesion of the foam to the hook and loop connector piece does not occur. On the contrary, often during the foaming-in process, the anchor elements prevent the foam material from flowing freely by the anchor elements, with the result that in the area of the anchor elements air holes occur in the foam, that is to say, cavities. These cavities in turn unintentionally promote the separation of the hook and loop connector piece and mold foam.